I was on my way home yesterday and I think I heard some detonation. It was when moderately accelerating and happened after each shift. It's hard to tell because of the resonating noise from the headers. Then when I get home I shut the truck off for a few minutes. I turned the key forward to let the pumps cycle and after the pump noise stopped I heard a bubbling noise coming from the fuel tank... Later on that evening I went to KFC to get some chow and when I was leaving the parking lot I was again moderately accelerating and my fuel pressure shot up to around 60 PSI with no change in acceleration.... Weird...

It hasn't done any of the above things again. I drove it all day today and there was no detonation, no bubbling in the tank, and I had an eagle eye on the fuel pressure gauge and it didn't fluctuate at all. Just normal fuel pressure.

What could have caused this and is there reason to be concerned?

 

im not sure if im saying this the right way, but when you step down on the throttle there is a relay,that raises the fuel presure ,60 should be at almost wot ,not at half throtle. the one time it happend ,was maybe the relay bumping it up prematurely, maybe someone elese can jump in . good luck

 

I don't know about your specific problem. However pinging right after a shift is common on a na car with it's timing too high or inadequate fuel.

I suppose low fuel pressure could cause the same thing? (too hot of a burn)

Rich

 

Well, it hasn't done it since that one time. I have a theory.... My engine runs a lot hotter now than it did before I went built. After the engine has run for a while I have noticed that my fuel rails are awefully hot when I touch them. My theory is that the fuel is getting heated up and the unused fuel is returning to the tank. Eventually it heats up the rest of the fuel and I have been told that the bigger fuel pumps don't like heat. This shouldn't be very common, but I was in traffic for like two hours and gave the truck ample time to heat up the fuel. Not to mention I had less than a quarter of a tank so there wasn't that much fuel to heat up.

That is the only thing I could think of because like I said, it hasn't done it since. I guess it was the heat....

 

I took a 69 Chevelle on Power Tour last year. It did the same thing. The chromed/polished ZL1 engine had the regulator on the back side of the rails so the fuel was heated by the engine/rails and then bypassed to the tank. Within a couple hours of driving it was sputtering or quitting altogether. The gas tank was super hot to the touch. As a quick fix 3000 miles from home we rigged up an ice chest with 20' of coiled copper tubing in it. I hooked the return line to that so the fuel ran through the ice chest filled with ice and copper tubing before returning to the tank. Cured the problem but went through several bags of ice a day as that fuel coming back is very hot.

The permanent solution is to have the fuel bypass before the rails so it's not heated. I know the factory setup does it in the rails, but the larger pumps we run add to the problem. Then get the tank low and I can see the issue happening again.